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Seedcorn Maggot

Seedcorn Maggot

Delia platura

Insectalso: Bean seed maggot

The small white maggots of a fly that attack germinating seeds and seedlings underground, hollowing out the seed before it can sprout. Seedcorn maggot is a common cause of poor, patchy stands in beans, corn, peas, cucurbits, and many other crops, especially in cool, wet springs and in soils rich in fresh organic matter.

🔎 How to spot it

The damage is underground and usually noticed as poor germination: gaps in the row, slow, spotty emergence, and seedlings that come up weak, with the growing tip eaten away producing bald snakehead plants. Dig up a failed seed and look for small, white, legless maggots, less than a quarter inch, with a pointed head, tunneling into it. The gray-brown adult fly resembles a small housefly.

🥀 Damage it causes

The maggots burrow into and hollow out planted seeds, destroying them before they germinate, and feed on the cotyledons and growing tips of those that do sprout, leaving stand gaps and stunted, deformed snakehead and Y-shaped seedlings that may die. Cool, wet conditions that slow germination give the maggots more time to do damage, worsening the loss.

🛡️ Prevent it

Because nothing can be done once the seed is attacked, all the management is before planting. Plow or disc under cover crops, weeds, and manure at least two weeks before sowing so the residue that attracts the egg-laying flies breaks down, and avoid heavy fresh manure. Plant into warm, well-drained soil under conditions that bring fast germination, and delay sowing in a cold, wet spring.

🧯 If it is already here

There is no rescue for attacked seed, so the response is to replant once conditions favor quick germination, ideally into warmer, drier soil so seedlings outrun the maggots. If a stand fails, wait for warmer soil and reseed, and adjust next time by working residue in earlier and planting when the soil is warm. Seed treatments are the main preventive where the pest recurs.

💡 Good to know

Seedcorn maggot damage is a planting-conditions story: it strikes hardest in cool, wet springs and in soil loaded with fresh, decaying organic matter that draws the flies to lay eggs. The practical defenses are all about timing, working residue in early and planting into warm soil for fast germination, since by the time you see the gaps, the maggots have moved on.

🌱 Plants it attacks

101 plants in the library can be attacked by this pest

Acorn SquashAdirondack Blue PotatoAdzuki Bean🥔All Blue PotatoAmbrosia CornArmenian CucumberAtlantic Giant PumpkinBeauregard Sweet PotatoBitter MelonBlack BeanBlack Beauty Zucchini🍉Black Diamond WatermelonBlack-Eyed PeaBloomsdale SpinachBlue Lake Green Bean🥒Boston Pickling CucumberBroad Windsor Fava BeanBull's Blood BeetButtercup SquashButternut SquashCannellini BeanCantaloupeCasaba MelonCharleston Gray WatermelonChioggia BeetCinderella PumpkinCipollini OnionCostata Romanesco ZucchiniCranberry BeanCrenshaw MelonCrimson Sweet WatermelonCupani Sweet PeaCylindra BeetDelicata SquashDetroit Dark Red Beet🥒Diva CucumberEdamameEgyptian Walking Onion🥒English CucumberEnglish Shelling PeaField PeaFingerling PotatoFordhook 242 Lima BeanGalia MelonGerman Butterball PotatoGolden Bantam CornGolden BeetHoneydew MelonHubbard SquashJack-O-Lantern Pumpkin🍉Jubilee WatermelonKabocha SquashKennebec PotatoKentucky Wonder Pole BeanKidney BeanKirby CucumberLemon CucumberLincoln PeaMalabar SpinachMarketmore Cucumber🍉Mini Love Watermelon🍉Moon and Stars WatermelonMung BeanNavy BeanNew Zealand SpinachNorland Potato🍉Orangeglo WatermelonPattypan SquashPearl OnionPersian CucumberPickling CucumberPinto Bean🌱Provider Bush Bean🥔Purple Majesty PotatoRed Noodle Yardlong Bean🧅Red OnionRed Pontiac PotatoRomano BeanRusset PotatoScarlet Runner BeanSilver Queen CornSnow Pea🥬Space SpinachSpaghetti Squash🧅Spanish OnionSugar Baby Watermelon🌱Sugar Daddy Pea🎃Sugar Pie PumpkinSugar Snap PeaSuyo Long CucumberTromboncino Squash🥬Tyee SpinachVidalia Sweet Onion🧅Walla Walla Sweet OnionWhite OnionWinter MelonYellow Crookneck Squash🍉Yellow Doll WatermelonYellow Summer SquashYellow Sweet Onion

For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.